TI-83 Plus Statistics 322
20. Press o to display the Y= editor.
Press | to move the cursor onto the = sign,
and then press Í to deselect Y1. Press }
Í to turn off plot 1.
21. Press q 9 to select 9:ZoomStat from the
ZOOM menu. The window variables are
adjusted automatically, and plot 2 is displayed.
This is a scatter plot of the residuals.
Notice the pattern of the residuals: a group of negative residuals, then a
group of positive residuals, and then another group of negative residuals.
The residual pattern indicates a curvature associated with this data set
for which the linear model did not account. The residual plot emphasizes
a downward curvature, so a model that curves down with the data would
be more accurate. Perhaps a function such as square root would fit. Try
a power regression to fit a function of the form y = a ä xb.
22. Press o to display the Y= editor.
Press ‘ to clear the linear regression
equation from Y1. Press } Í to turn on
plot 1. Press ~ Í to turn off plot 2.